Key controlled pulse generator

ABSTRACT

The invention relates to a key controlled pulse generator which generates a pulse in a coil surrounding a core in a self selfenergized circuit, the magnetic circuit having a gap therein which is reduced or increased by means of a bistable armature whose movement is initiated by a key. The bistable armature may be provided with an overcenter spring and the gap in the magnetic circuit may be defined by the core and the armature. A shim of nonmagnetic or nonmagnetizable material may be positioned on the armature so as to prevent contact in the magnetic sense between the armature and the coil core. A second magnetic circuit may be provided in which a gap is reduced by the armature when moving in the opposite direction to that in which it reduces the gap in the other magnetic circuit.

United States Patent [72] Inventor Otto Carl Selden 72 Emlyn Road, London, England [21] App1.No. 844,361 [22] Filed July 24, 1969 [54] KEY CONTROLLED PULSE GENERATOR 4 Claims, 4 Drawing Figs.

[52] US. Cl 310/15, 310/29; 335/230 [51} Int. Cl H0211 35/06 150 Field ofSearch 310/12, 14, 15, 30, 29, 3639; 335/229, 230, 274; 200/67; 307/106 [56] References Cited UNITED STATES PATENTS 2,135,843 11/1938 Pye 310/36 2,376,557 5/1945 Severance 310/36 3,315,104 4/1967 Barr ABSTRACT: The invention relates to a key controlled pulse generator which generates a pulse in a coil surrounding a core in a self energized magnetic circuit, the magnetic circuit having a gap therein which is reduced or increased by means of a bistable armature whose movement is initiated by a key. The bistable armature may be provided with an overcenter spring and the gap in the magnetic circuit may be defined by the core and the armature. A shim of nonmagnetic or nonmagnetizable material may be positioned on the armature so as to prevent contact in the magnetic sense between the armature and the coil core. A second magnetic circuit may be provided in which a gap is reduced by the armature when moving in the opposite direction to that in which it reduces the gap in the other magnetic circuit.

KEY CONTROLLED PULSE GENERATOR BACKGROUND OF THE INVENTION This invention relates to a key controlled pulse generator and is particularly suitable for use in keyboards which, for example, form input devices for data processing machines.

The input data are usually available in the form of characters, for instance decimal numerals, while the data processing machine is usually adapted to process these characters in binary coded forrn. The input of the data is effected as a rule by means of a key board and each key of the key board is associated with a coding circuit which it energizes when the key in depressed and which converts the character associated with the key in question into a combination of binary digits. The energization of the coding circuit is effected by means of a mechanical electric switch which is actuated when the associated key is depressed and which connects the coding circuit to a current source.

It has been found that key operated mechanical switches are not sufficiently reliable in service. They are subject to. wear and often fail to establish the required contact due to dust and dirt.

SUMMARY OF THE INVENTION It is an object of the invention to provide a pulse generator suitable for taking over the functions of the known mechanical switching arrangements for keyboard operation.

According to the invention, a key controlled pulse generator comprises a magnetic circuit including a permanent magnet, a core,'a coil surrounding the core in which pulses are to be generated on variation of the magnetic flux in the magnetic circuit, and a bistable pivotable armature whose pivot point lies in the magnetic circuit and which is pivotable to reduce or increase a gap in the magnetic circuit and a key for initiating movement of the armature from one bistable position to the other bistable position.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail by way of example with reference to the accompanying drawings, in which:

FIG. 1 is an elevation view of a key operated pulse generator in accordance with the invention;

FIG. 2 is a sectional view taken on the line II-II of FIG. 1;

FIG. 3 is an elevation view taken in the direction of the arrow III of FIG. 2, and

FIG. 4 shows a modified construction of pulse generator, with the operating key omitted.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 to 3 of the drawings, a key controlled pulse generator comprises a frameworkincluding a top plate I, of nonmagnetic material, and a bottom plate 2, of soft magnetic material, jointed together by means of two brass bolts 3 surrounded by brass spacer sleeves 4 and retained by nuts 5. A core 6, which is a press fit into the bottom plate 2 and which is of soft magnetic material, is surrounded by a coil 8 in which a pulse is to be generated, the pulse being fed to, for example, a coding circuit (not shown) by means of leads 10.

Also supported on the base member 2 is a permanent magnet 12 bolted to the base plate 2 by means of a brass nut and bolt l4, 15. A variable shield 17 is mounted for sliding up and down the permanent magnet 12 (FIG/l). An extension piece 19, also of soft magnetic material, is bolted by means of the bolt 14 to the top of the permanent magnet. An armature 20 is pivoted at 22 to the projection 19 and is pivotable about this pivot point 22 towards and away from the core 6 of the coil 8. An over-center spring 23 is provided and this makes the armature 20 bistable.

Thus a magnetic circuit is formed consisting of the core 6, the bottom plate 2, the permanent magnet 12, the extension 19 and the armature 20. The magnetic circuit has a gap therein defined by the end 24 of the core 6 and the end 25 of the armature 20. The armature is provided with a brass shim 41 to prevent magnetic contact between the armature 20 and the coil 8. I

A key 28 is mounted on a slide 29 which passes through a slot 30 in the top plate 1 and a slot 31 in the bottom plate 2. This slide is thus mounted for vertical movement (FIG. 1) and this vertical movement is limitedin the upward sense by a lug 33 which engages the top plate 1 and in the downward sense by means of a lug 34 which engages the bottom plate 2. Movement of the slide in a downward direction is achieved by an operator depressing the key while movement of the slide in the upward direction is achieved by means of a return spring 36 which is connected between the lug 34 and the top plate 1. The slide is provided with a recess 38 into which a projection 40 on the armature 20 projects with clearance.

The operation of the key controlled pulse generator as shown in FIGS. 1 to 3 will now be described:

With the parts of the device as shown in FIG. I, the gap in the magnetic circuit is fully open. To cause a pulse to be produced in the coil 8, the operator depresses the key 28 moving the slide 29 downwards against the action of the return spring 36. This downward movement of the slide is initially a lost motion movement until the edge of the recess 38 engages the projection 40 on the armature 20. The armature 20 is thus pushed downwards until it moves past its center position, whereupon it will continue to travel downwardly under the action of its over-center spring 23 and the pull of the magnetic flux until the shim 41 engages the core 6. The recess 38 is of a sufficient size to permit this movement of the armature after passing its center position without any engagement taking place between them.

This movement of the armature 20 causes a change in flux in the magnetic circuit which, as previously mentioned, consists of the core 6, bottom plate 2, permanent magnet 12, projection 19 and armature 20 and so generates a pulse in the coil 8 which is transmitted down the line 10 to the coding circuit or other following equipment.

Because the effective movement of the armature 20 which causes the generation of the pulse takes place entirely under the action of the over-center, spring 23 and the magnetic flux appearing in the gap between the armature 20 and the core 6, the pulse which is generated will be the same each time the key is depressed irrespective of whether the key is depressed quickly or slowly.

As soon as the key is released, the return spring 36 will return the slide to its original position ready for the next operation of the key. During this return motion of the slide, it will first take up lost motion between it and the armature 20 and will then move the armature over its center position whereupon it is returned to its initial position under the action of the over-center spring 23.

It will, of course, be appreciated that the armature will generate a further pulse in the coil 8 during this returnmovement, but in the opposite sense. However, since the pulse producing movement of the armature is in this case controlled by the slide, there is a tendency for such pulses to be smaller and to vary between different operations of the key due to variations in the release of the key by the operator. This pulse would therefore not be used and can be suppressed in the following circuitry. The brass shim 41 provided on the armature ensures that complete magnetic closure of the magnetic circuit does not take place and thus enables the armature to be returned with a relatively small application of spring pressure. Adjustment of the magnetic circuit is provided by the shield 17 which can be slid vertically on the permanent magnet 12. By means of this adjustment, the magnitude of the pulse produced can be controlled and this adjustment will also determine the return force required to be applied to the armature 20.

It has been found that a current pulse produced by the downward operation of the key is strong enough to operate about 10 electronic switches which may form part of the coding circuit. It will be appreciated that, as a result, no current source is required either for the production of the pulse or for the conversion of the character into a coded combination of pulses such as required by data processing machines. The use of mechanical switches are obviated and thus a more reliable operation is produced which is not jeopardized by the infiuence of dust and dirt.

' FIG. 4 shows a modification of the arrangement of FIGS. 1 to 3 in which it is possible to produce a consistent pulse both on the depression of the key and during its return. For this purpose an additional coil 8a having a core 60 is provided. The operation of the device for the production of the downward pulse by means of the coil 8 is the same as that FIGS. 1 to 3. However, during the return stroke, use is made of the movement of the armature 20, after its center point has been reached, to narrow the gap between it and the core 6a. In this way a pulse can be generated in the coil 80 using a magnetic circuit consisting of the core 6a, the bottom plate 2, the permanent magnet 12 the extension 19 and the armature 20. Once again, because the pulse creating movement of the armature 20 is independent of the operation of the slide, consistent pulses will always be obtained on the return movement of the armature 20 and nonstandard pulses which are produced in the opposite sense during the forward movement of the armature can be suppressed. Likewise an additional shim 41a is provided on the top of the armature where it engages the core 6a.

lclaim:

l. A key controlled pulse generator comprising, in combination, a magnetic circuit including a permanent magnet, a core substantially parallel to said permanent magnet, a coil surrounding said core and having pulses generated therein upon variation of the magnetic flux in said magnetic circuit, and a bistable pivotable armature positioned across said permanent magnet and said core and having a pivot point lying in said magnetic circuit, said armature being pivotable to reduce or increase a gap in said magnetic circuit; an over-center spring operatively connected to said armature and operable to bias said armature to either of its bistable positions; a slide extending substantially parallel to said permanent magnet and movable between a first position and a second position; a single key on said slide for manual operation to move said slide from said first position to said second position; spring means biasing said slide from said second position to said first position on release of said key; first engagement means on said slide spaced from said armature in said first position of said slide and engageable with said armature upon movement of said slide from said first position toward said second position, to initiate movement of said bistable armature from a first stable position to a second stable position; second engagement means on said slide spaced from said armature in said second position of said slide and engageable with said armature during movement of said secondposition to a said first post position to initiate movement of said bistable armature from said secondstable position to said first stable position; and over-center means. including said over-center spring, operatively associated with said bistable armature and operable, upon initiation of movement of said bistable armature from said first position to said second position. responsive to operation of said slide, to complete movement of said bistable armature to said second stable position and operable, upon initiation of movement of said bistable armature from said second stable position to said first stable position to complete movement of said bistable armature to said first stable position.

2. A key controlled pulse generator, as claimed in claim 1. including a shield mounted on said permanent magnet for a slidable adjustment therealong.

3. A key controlled pulse generator, as claimed in claim 1, in which said bistable pivotable armature has said pivot point at one end and has a free end spaced from said pivot point; said gap in said magnetic circuit being defined by said free end of said armature and said core; and a second magnetic circuit including said permanent magnet said bistable pivotable armature, said pivot point, a second core extending parallel to and adjacent said first mentioned core and having a portion extending beyond said first mentioned core and into a position in which it defines, with said free end of said bistable pivotable armature, a gap in said second magnetic circuit which is reduced by pivoting of said armature from said second stable position to said first stable position, and a second coil surrounding said second core and having pulses generated therein responsive to variation of the magnetic flux in said second magnetic circuit; said second magnetic circuit operating as part of said over-center means to complete a said movement of said bistable armature from said second stable position to said first stable position.

4. A key controlled'pulse generator, as claimed in claim 3, including a shield mounted on said permanent magnet for adjustment therealong. 

1. A key controlled pulse generator comprising, in combination, a magnetic circuit including a permanent magnet, a core substantially parallel to said permanent magnet, a coil surrounding said core and having pulses generated therein upon variation of the magnetic flux in said magnetic circuit, and a bistable pivotable armature positioned across said permanent magnet and said core and having a pivot point lying in said magnetic circuit, said armature being pivotable to reduce or increase a gap in said magnetic circuit; an over-center spring operatively connected to said armature and operable to bias said armature to either of its bistable positions; a slide extending substantially parallel to said permanent magnet and movable between a first position and a second position; a single key on said slide for manual operation to move said slide from said first position to said second position; spring means biasing said slide from said second position to said first position on release of said key; first engagement means on said slide spaced from said armature in said first position of said slide and engageable with said armature upon movement of said slide from said first position toward said second position, to initiate movement of said bistable armature from a first stable poSition to a second stable position; second engagement means on said slide spaced from said armature in said second position of said slide and engageable with said armature during movement of said second position to a said first post position to initiate movement of said bistable armature from said second stable position to said first stable position; and over-center means, including said over-center spring, operatively associated with said bistable armature and operable, upon initiation of movement of said bistable armature from said first position to said second position, responsive to operation of said slide, to complete movement of said bistable armature to said second stable position and operable, upon initiation of movement of said bistable armature from said second stable position to said first stable position to complete movement of said bistable armature to said first stable position.
 2. A key controlled pulse generator, as claimed in claim 1, including a shield mounted on said permanent magnet for a slidable adjustment therealong.
 3. A key controlled pulse generator, as claimed in claim 1, in which said bistable pivotable armature has said pivot point at one end and has a free end spaced from said pivot point; said gap in said magnetic circuit being defined by said free end of said armature and said core; and a second magnetic circuit including said permanent magnet, said bistable pivotable armature, said pivot point, a second core extending parallel to and adjacent said first mentioned core and having a portion extending beyond said first mentioned core and into a position in which it defines, with said free end of said bistable pivotable armature, a gap in said second magnetic circuit which is reduced by pivoting of said armature from said second stable position to said first stable position, and a second coil surrounding said second core and having pulses generated therein responsive to variation of the magnetic flux in said second magnetic circuit; said second magnetic circuit operating as part of said over-center means to complete a said movement of said bistable armature from said second stable position to said first stable position.
 4. A key controlled pulse generator, as claimed in claim 3, including a shield mounted on said permanent magnet for adjustment therealong. 